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Nitrate Removal in Two Relict Oxbow Urban Wetlands: A 15N Mass-balance Approach
Citation:
Harrison, M. D., P. M. Groffman, P. M. MAYER, AND S. S. Kaushal. Nitrate Removal in Two Relict Oxbow Urban Wetlands: A 15N Mass-balance Approach. BIOGEOCHEMISTRY. Springer, New York, NY, 111(1-3):647-660, (2012).
Impact/Purpose:
Journal Article for Biogeochemistry
Description:
A 15N-tracer method was used to quantify nitrogen (N) removal processes in two relict oxbow wetlands located adjacent to the Minebank Run restored stream reach in Baltimore County (Maryland, USA) during summer 2009 and early spring 2010. A mass-balance approach was used to determine the flow of 15NO3- to plants, algae, sediments and denitrification (unaccounted 15NO3-). During the summer, plant and algal uptake accounted for 42% and denitrification 57%, of the added 15NO3- in oxbow 1, with less than 1% remaining in the water column and in sediments. In oxbow 2 during the summer, plant and algal uptake accounted for 63% and denitrification 38% of the added 15NO3-, with < 1% remaining in the water column and in sediments. During the early spring, plant and algal uptake were much lower in both oxbows, ranging from 0.05 to 13.3%, and denitrification accounted for 97% and 87% of the N removed, respectively. The amount of 15N removed by denitrification corresponded to an areal NO3- removal rate of 12 mg N m-2 d-1 and 6 mg N m-2 d-1 in the summer and 78 mg N m-2 d-1 and 15 mg N m-2 d-1 in the spring, in oxbow 1 and oxbow 2, respectively. Our results suggest that the two relict oxbow wetlands are sinks for NO3- during both summer and spring but that the pathways of removal vary with plants and algae playing a major role in summer but not in spring.
